1. Field of the Invention
The invention relates to a lock mechanism for locking a first apparatus and a second apparatus, an external apparatus provided with the same and connected to an image forming apparatus main body, and an image forming apparatus provided with the same.
2. Related Background Art
For example, there are many image forming apparatuses designed to permit the additional provision of a sheet feeding apparatus for making the sheet feeding capacity thereof large, an external discharging apparatus for increasing the discharged sheet stacking capacity, or an external apparatus' such as an original reading apparatus for increasing the function of the apparatus.
These external apparatuses are usually installed below or above an image forming apparatus main body, and it is often the case that a plurality of external apparatuses are usable in piles.
When these external apparatuses are connected to the image forming apparatus increases, and in order to secure the stability of the apparatus at this time, and to satisfy the standards of stability determined by Underwriters Laboratories (UL), Canadian Standards Association (CSA), etc., it is often necessary to couple the apparatuses together so as not to be spaced apart from each other. When the two apparatuses are thus to be coupled together so as not to be spaced apart from each other, the apparatuses have been coupled together as by a method of fixing the apparatuses by screws, as disclosed, for example, in Japanese Patent Application Laid-Open No. H06-032470 (page 3).
Also, as a construction for locking the apparatuses, there is a construction disclosed, for example, in Japanese Utility Model Application Laid-Open No. H05-084762. In a mechanism for locking the apparatuses with the door of an electronic apparatus, as disclosed in Japanese Utility Model Application Laid-Open No. H05-084762, a stopper is engaged with a pin, whereby the door is locked. When the door is to be opened, when an operator rotates the stopper, the stopper is restrained in a lock releasing position by a part (leaf spring) for maintaining a lock released state. In operative association with the operation of opening the door, the stopper is moved from the lock releasing position to a lock position.
In the apparatus for coupling the apparatuses together by the screws as disclosed in Japanese Patent Application Laid-Open No. H06-032470 (page 3), it is necessary to perform an operation such as screwing after the two apparatuses have been installed adjacent to each other. Consequently, the work for coupling the apparatuses together has been cumbersome. Also, when the apparatus main body is to be moved or the external apparatus is to be replaced with another one, it is necessary to release the mounting of the two apparatuses and space them apart from each other, but if the apparatuses are fixed by the screws or the like, the apparatuses cannot be easily detached from each other, and the working property has been bad.
Also, in a lock mechanism wherein the stopper is moved from the lock releasing position to the lock position in operative association with the operation of spacing the two apparatuses apart from each other (this is disclosed in Japanese Utility Model Application Laid-Open No. H05-084762), there is the problem that when the two apparatuses are spaced apart from each other, the stopper contacts with the pin to thereby hamper the spacing apart of the two apparatuses.
The embodiment shown in Japanese Utility Model Application Laid-Open No. H05-084762 is a form in which the door is pivotally moved about a shaft provided in the main body and therefore, the locus of the door when the door is opened is always substantially the same relative to the main body and thus, this problem is not remarkable. However, when an attempt is made to apply the lock mechanism of Japanese Utility Model Application Laid-Open No. H05-084762, for example, to a construction in which the two apparatuses are independent of each other, when one apparatus is to be spaced apart from the other apparatus, one apparatus may sometimes be spaced apart from the other apparatus in an inclined state with respect to the latter. In such a state, the timing at which the stopper being in the lock releasing position is moved away from the part for maintaining the lock released state to the lock position quickens, and the above-noted problem that the stopper contacts with the pin to thereby hamper the spacing apart of the two apparatuses becomes great. Further, in a case where in order to lock the two apparatuses reliably, a plurality of stoppers for locking are provided and the plurality of stoppers are moved as a unit, the above-noted problem becomes more remarkable.